There are numerous advantages in using narrow size range ceramic powders as starting materials, including uniform microstructures leading to optimal performance properties. One method of producing narrow size materials is by a centrifugal classification system, described in the above application. One of the problems encountered in making narrow size range powders in this fashion, is that the resulting powder is dilatent and quite difficult to remove from the centrifuge bowl, often requiring the powder to be chiseled out in a batch mode. The dilatent aspect of the powder prevents continuous classification to be carried out using conventional equipment, such as an auger-type implement which empties the bowls.